1. Field of the Invention
The present invention relates to a method which can precisely measure temperature of an object in a noncontacting manner using a radiation thermometer over a wide temperature range from low to high temperature without having to setting the emissivity of the object. The present invention also relates to a temperature-measuring device implementing the method.
2. Description of the Related Art
In order to measure the true temperature of an object surface in a noncontacting manner, it is important that the emissivity of the object, which is one of thermal properties, and its temperature dependency are exactly determined. The measurement accuracy of a noncontact radiation thermometer highly depends on whether the emissivity is correctly set or not.
Known radiation thermometers are provided with emissivity setting dial for setting emissivity of an object to be measured. The emissivity is determined by adjusting this dial, and the temperature is measured based on this emissivity. However, the temperature of an object is not always measured in consideration of exact temperature dependency of the emissivity of the object. Therefore, in some cases, the emissivity is separately determined before the measurement of temperature. In such cases, the advantage of radiation thermometers, i.e., simple measurement in a noncontacting manner, is attenuated.
In two-color radiation thermometers, the setting of emissivity is not required in the measurement of an object of a greybody surface. However, the setting of emissivity is necessary in the measurement of surface temperature of objects other than greybodies. In addition, in known radiation thermometers, temperatures over a wide range from a low- (about −50 to 0° C.) and a middle-temperature (from about room temperature to 600° C.) to a high-temperature (600 to 3000° C.), cannot be measured by a single thermometer, because of the restriction caused by the characteristics and sensitivities of a temperature sensor. Consequently, a plurality of radiation thermometers is necessary for measuring temperatures over a wide range.